1. Field of the Invention
The invention relates to ribbon cartridges which utilize a capstan to advance the ribbon in the cartridge, and in particular those cartridges which are used in typewriters and printers.
2. Description of the Prior Art
The use of capstans to advance a ribbon in a cartridge has long been known in the art. Prior art devices may use either single or double capstans with idlers to advance the ribbon. These prior art capstans are either permanently housed within the cartridge or form an integral part of the machine which utilizes the cartridge itself.
Examples of prior art cartridges are numerous. U.S. Pat. No. 3,411,731 to Kelly discloses a tape cartridge having a single capstan permanently housed within the tape cartridge. U.S. Pat. No. 3,884,430 to Martin and U.S. Pat. No. 4,191,984 to Tsukidate et al. disclose tape cassettes having no capstans or idlers housed in the tape cartridge, instead advancing the tapes with capstans and idlers integral to the machines utilizing the cassettes. U.S. Pat. No. 4,093,151 to Karsh discloses yet another variation wherein the capstans used to advance the tape are an integral part of the machine utilizing the cassette, but idlers permanently mounted within the cassette are used to urge the tape against the capstans.
Ribbon cartridges utilized in printer applications have capstans permanently housed in the cartridge, since printers typically do not have capstans and idlers as integral parts of the printers themselves. The capstans in such ribbon cartridges have means for engaging a drive mechanism in the printer which is used to rotate the capstans. Examples of such ribbon cartridges include U.S. Pat. No. 4,034,935 to Plaza et al. and U.S. Pat. No. 4,496,255 to Meintrup et al.
Plaza et al. discloses a single pass ribbon cartridge having a capstan permanently housed in the cartridge casing. A disadvantage of such cartridges is that the cartridges are limited to use with printers that have the specific drive mechanism designed to engage the capstan housed in the cartridge casing. In addition, the speed at which the tape advances in the cartridge is determined by the circumference of the particular capstan housed in the casing. As a result, an entirely new cartridge must be manufactured for printers differing only in the configuration of the engaging portion of the printer drive mechanism or the rotational speed of the printer drive mechanism.
Meintrup et al. discloses an invertible ribbon cartridge utilizing two capstans permanently housed within the ribbon cartridge casing. Although Meintrup et al. requires two capstans in the ribbon cartridge, only one capstan at a given time is used to advance the ribbon. Meintrup et al. thus has the disadvantage of requiring the assembly of more parts than are necessary to advance the ribbon at a given time, in addition to the disadvantages previously mentioned for Plaza et al.
A prior art multistrike ribbon cartridge marketed by NEC Corporation utilizes the dual capstan arrangement disclosed in Meintrup et al. In addition, the NEC cartridge has a pair of capstan idlers mounted on a slidable bar and capstan pulleys attached to a portion of the capstans extending beyond the faces of the cartridge. While this combination permits the capstans to alternately engage the ribbon, the NEC device still suffers from the disadvantages of Meintrup et al., since the capstans themselves are permanently housed within the cartridge casing.
In view of the above disadvantages of the prior art, an object of the present invention is to allow a universal ribbon cartridge to be used with printers differing only in configuration and rotational speed of their cartridge drive mechanisms by simply changing capstans in the universal cartridge.
A further object of the invention is to reduce assembly costs of dual capstan or invertible ribbon cartridges by using a single capstan in the cartridge, and thereby eliminating one of the capstans with its associated parts.